A Danio That Nips

jaimiemay

Hey; My tank is cycled and recently I had my mother purchase me 2 zebra danios randomly....Before placing them in my tank I confirmed they were community fish and all has been well but I guess that one of them has become very well established in the tank that also has guppies/platies in it. I noticed that the other danio had begun looking a little raggard compared to the other one (my guess is he picks on him too) and when I woke this morning I seen the aggressive danio nip one of my male guppes tail.
I'm now annoyed because I love my guppies and bred that male from a fry ;[ he isn't that well probably because I just realized what was going on.
Well...I know danios are schooling fish and i was planning on adding 2 more danios to the tank to make it a little more 'schooly' but now I'm not sure if this will make them peaceful or more aggressive to the other tank memebers. The one danio isn't picking on anybody, just the one.
Do you guys think that this will help the problem or make it worse?
Advice?

bettababy

How big is the tank? How many fish total are in it currently? (please list how many of each species)

Danios are noted for their nipping, they can be somewhat aggressive depending on the number in their school, size of the tank, amount of decor in the tank, and water conditions, and what other fish they are mixed with.

Adding 2 more danios should be determined based on space/tank size and population, and it may or may not resolve the problem. A group of 4 is still small for a school. If you can answer the questions I have asked and provide more information on the overall tank situation, it would be much easier to help you.

Please be forewarned, it is possible for any species of fish to find an aggressive fish that just does not work out in a community situation. Some of these kinds of problems can be individual personalities, which all fish have (just like people).

In the mean time, it would be a good idea to move the aggressive fish to quarantine, or to move the injured/damaged fish to quarantine to help ensure infection does not set in until it is healed. Keeping water params in pristine condition is also very important.

Can you post a clear photo of your tank? That will give us the ability to see if decor is an issue, at which time we can offer suggestions on changes that will help resolve your situation.

jaimiemay

20 gallons, been running for approx a year/ water parameters are in check except I have fairly high KH but hasn't seemed to affected the fish all that much.
The tank isn't overcrowded (at least according to the guy at the fish store). I have 2 platies, 6 guppies in total (the one who has been nipped moved quartentine) and the 2 danios.
As for the decor I have a air pump in the corner for them, a medium sized cave, small maui head and a few fake plants in there.
I will take an updated photo.

Thank you :)

bettababy

Can you please post the numbers for ammonia, nitrite, nitrate, pH and KH? Telling us that they are "in check" doesn't tell us anything at all. Knowing the exact numbers helps us not only to identify if one or 2 things are off, but how all of those things are working together, which is very important.

jaimiemay

Can you please post the numbers for ammonia, nitrite, nitrate, pH and KH? Telling us that they are "in check" doesn't tell us anything at all. Knowing the exact numbers helps us not only to identify if one or 2 things are off, but how all of those things are working together, which is very important.

nitrites are 0. nitrate 20. pH-8 KH- 240
The last time I checked the ammonia which about 2 weeks ago was at 0 too, I don't have anything to test it atm

beachcire

Your numbers look o.k. Danios like a lower PH but as long as it is steady you should be fine. You could add up to 3 more danios in my opinion as long as you have adequate filtration and maintain a good water change regiment. That should help to spread out the aggression of your current danios.

I like to check stocking levels at AqAdvisor - Intelligent Freshwater Tropical Fish Aquarium Stocking Calculator and Aquarium Tank/Filter Advisor. It is a great tool that will help you figure out what will work in a particular tank. It is not the gospel but it does have a lot of useful information.

I have never kept guppies but I have heard that they tend to like somewhat brackish water. Do you keep salt in your tank?

jaimiemay

thanks for the reply and thanks for the link, wonderful site & I will be using it in the future :)
I havn't used aquarium salt the entire time I have had platies/guppies....not sure if it made much of a difference or not but I recently purchased some aquarium salt and have been using it.

Byron

I strongly recommend you not use salt. While livebearers can tolerate it (due to their preference for harder water) many naturally soft water fish cannot, to varying levels. As a general practice, salt should never be added to a freshwater aquarium except as a specific treatment and then only if the fish in the tank can tolerate it.

The following is from my post in another thread on salt, copied for your information:

Salt is detrimental to freshwater fish and plants in varying degrees. To understand why, we must understand what salt does in water.

Salt makes the water more dense than the same water without salt. The aquarium contains water. The bodies of fish and plant leaves also contain water [just as we do--we are, what is it, 90-some percent water?]. The water in the aquarium and the water in the fish/plant are separated by a semi-permeable layer which is the cell. Water can pass through this cell. When either body of water is more dense, the other less-dense body of water will pass through the membrane to equalize the water on both sides.

Water is constantly passing through the cells of fish by osmosis in an attempt to equate the water inside the fish (which is more dense) with the water in the aquarium. Put another way, the aquarium water is diluting the fish's body water until they are equal. Freshwater fish regularly excrete this water through respiration and urination. This is the issue behind pH differences as well as salt and other substances. It increases the fish's work--the kidney is used in the case of salt--which also increases the fish's stress in order to maintain their internal stability. Also, the fish tends to produce more mucus especially in the gills; the reason now seems to be due to the irritant property of salt--the fish is trying to get away from it.

I have an interesting measurement for fish. Dr. Stanley Weitzman, who is Emeritus Research Scientist at the Department of Ichthyology of the Smithsonian Institute in Washington and an acknowledged authority on characoid fishes, writes that 100 ppm of salt is the maximum for characins, and there are several species that show considerable stress leading to death at 60 ppm. 100 ppm is equal to .38 of one gram of salt per gallon of water. One level teaspoon holds six grams of salt, so 1 tsp of salt per gallon equates to more than 15 times the tolerable amount. Livebearers have a higher tolerance (mollies sometimes exist in brackish water) so the salt may be safe for them.

Plants: when salt is added to the aquarium water, the water inside the plant cells is less dense so it escapes through the cells. The result is that the plant literally dries out, and will wilt. I've so far been unable to find a measurement of how much salt will be detrimental to plants; all authorities I have found do note that some species are more sensitive than others, and all recommend no salt in planted aquaria.

From my fairly extensive research, I have never found a leading ichthyologist who has not advised that salt should never be routinely added to a freshwater aquarium.